Mother-to-child transmission of human T-lymphotropic virus type I (HTLV-I): an extended follow-up study on children between 18 and 22-24 years old in Okinawa, Japan.

The significant difference observed between the seroprevalence of HTLV-I in adults and in children is as yet unexplained. To evaluate a hypothetical explanation of the existence of seroconversion cases of "seronegative carriers" for this phenomenon, 21 of 55 children who had been born to seropositive mothers and who remained seronegative until the age of 18 years were further followed up at the ages of 22 and/or 24 years. None of the 21 seronegative children born to seropositive mothers seroconverted, either at 22 years or at 24 years. In addition, the polymerase-chain-reaction (PCR) technique could not prove the existence of the HTLV-I provirus genome in peripheral mononuclear cells (PBMC) of 10 of these children. Our results fail to prove the possibility of viral latency of HTLV-I in mother-to-child transmission. Therefore, the hypothetical seroconversion of "seronegative carriers" after adulthood cannot be an explanation.